(a) Field of the Invention
This invention relates to a testing device for containers used in the beverage and food industry and more particularly, but not by way of limitation, to a container end testing device for testing the surface area of a container end prior to the sealing of the container end to the container.
(b) Discussion of Prior Art
Today, millions of cans of soft drinks, beer and other products are sold each day. Most of these containers include a pull tab with a score line defining an opening in a container end. The pull tab is used for creating an opening in the container end. Because of the score line and the pull tab, careful control of the forming operation of the container end must be maintained in order that each container can be opened with little effort and still not leak under internal pressure from the carbonation of the product stored inside the container.
Heretofore, there have been a variety of different types of container testing devices and apparatus for testing for leaks in container ends.
In U.S. Pat. No. 4,440,016 to Konagaya, et al., a method for high-speed leak testing of container ends is disclosed. The method of this invention is achieved by the use of a closed chamber which encloses the container end therein. Pressurized air is injected into the upper closed portion of the chamber to test whether the container end has a leak by measuring the corresponding change in air pressure within the closed portion of the chamber. This reference is representative of prior art references which utilize standard O-rings to seal the container end.
In U.S. Pat. No. 3,399,563 to Helms, a method and apparatus for leak testing container ends is also described. This reference makes use of standard O-rings for sealing the container end within the test chamber. The primary relevance of this reference is that a sensing element is placed directly adjacent the testing chamber in order to detect a change in environmental conditions which indicates a leaking container end. More specifically, the sensor in this invention detects high frequency vibrations caused by high pressure air leaking through the container end.
In U.S. Pat. No. 4,495,797 to Cassell, Jr., et al., an apparatus for leak testing container ends is disclosed. This reference is also representative of testing devices which incorporate standard O-rings and use of a pressure transducer which is remote from the testing chamber. A positive control feed mechanism is used to introduce the container ends into the testing chamber.
In U.S. Pat. No. 4,096,736 to Moshier, an ultrasonic leak detection apparatus and method is described. The primary relevance of this reference is the disclosure of a flat surface to seal the container end within the testing chamber, as opposed to the use of standard O-rings.
In U.S. Pat. No. 5,042,289 to Jensen, the use of a flat surface to seal the container end is disclosed. This reference discloses air pressure applied to one side of the container end, and such pressure is used to seal the annular peripheral rim of the opposite face of the container end against a flat seal to establish a seal without gripping or otherwise contacting the container end.
In U.S. Pat. No. 3,954,003 to Dobbins, yet another container end tester is described utilizing pressurized air. This reference emphasizes the use of a seating means in conjunction with a reciprocating pin in order to stabilize the container end being tested.
In U.S. Pat. No. 3,792,606 to Munger a leak detection apparatus is described which teaches the use of a flat seal and a sensing element which is directly mounted to the testing chamber. However, in this case, leak detection is achieved not by a pressure transducer but through a diaphragm which senses vibrations created by pressurized air which may leak through the container end.
In U.S. Pat. No. 5,086,653 to Bagwell, an apparatus for measuring forces applied to a pull tab of a container end during the formation of an opening in the container is disclosed. Although this reference does not disclose a device used for leak testing, it discloses the use of a gravity feed chute 12 in order to introduce container ends into the apparatus.
U.S. Pat. No. 3,499,314 to Robert, et al., is representative of another type of device used for leak testing container ends, and U.S. Pat. No. 5,123,278 to McKittrick discloses a pressure tester and method for buckle testing of containers.
Perhaps the most relevant prior art reference is a container tester called a "SPOT" machine which is manufactured by the subject assignee, Conal Engineering Inc., Golden, Colorado for Metal Container Corp. The "SPOT" machine uses a double stroking cylinder in order to bring the testing pocket down while the subject container end testing device utilizes a single stroke cylinder to bring a lower housing upwards for engaging the container end to be tested. The "SPOT" machine utilizes a four-pin arrangement to guide and stabilize the container end while the testing device described herein utilizes a three-pin arrangement with a retractable stop pin and two stationary guide pins. Further, the "SPOT" machine has a transducer remote from the testing chamber while subject invention has a pressure transducer placed directly next to the testing chamber.
None of the above mentioned patents and prior art container end testing devices have the advantages and unique combination of features, structure and function when compared to the subject container end leak testing device as described herein.